The folks at Resume Play had some hands-on time with Fallout: New Vegas.

In Hardcore Mode you’ll experience hardship through New Vegas as everything in the game is heightened to intense realism. Your ammunition now adds weight, and you’re forced to actually consume water regularly to avoid dehydration or death. Your healing after usage of the stimpak (health units) is now delayed, and to heal crippled limbs you need a high level in your medicine skill.